Arsenic-induced IGF-1 signaling impairment and neurite shortening: The protective roles of IGF-1 through the PI3K/Akt axis.

We recently reported that arsenic caused insulin resistance in differentiated human neuroblastoma SH-SY5Y cells. Herein, we further investigated the effects of sodium arsenite on IGF-1 signaling, which shares downstream signaling with insulin. A time-course experiment revealed that sodium arsenite began to decrease IGF-1-stimulated Akt phosphorylation on Day 3 after treatment, indicating that prolonged sodium arsenite treatment disrupted the neuronal IGF-1 response. Additionally, sodium arsenite decreased IGF-1-stimulated tyrosine phosphorylation of the IGF-1 receptor ß (IGF-1Rß) and its downstream target, insulin receptor substrate 1 (IRS1). These results suggested that sodium arsenite impaired the intrinsic tyrosine kinase activity of IGF-1Rß, ultimately resulting in a reduction in tyrosine-phosphorylated IRS1. Sodium arsenite also reduced IGF-1 stimulated tyrosine phosphorylation of insulin receptor ß (IRß), indicating the potential inhibition of IGF-1R/IR crosstalk by sodium arsenite. Interestingly, sodium arsenite also induced neurite shortening at the same concentrations that caused IGF-1 signaling impairment. A 24-h IGF-1 treatment partially rescued neurite shortening caused by sodium arsenite. Moreover, the reduction in Akt phosphorylation by sodium arsenite was attenuated by IGF-1. Inhibition of PI3K/Akt by LY294002 diminished the protective effects of IGF-1 against sodium arsenite-induced neurite retraction. Together, our findings suggested that sodium arsenite-impaired IGF-1 signaling, leading to neurite shortening through IGF-1/PI3K/Akt.

Safety Evaluation of the Polyherbal Formulation NawaTab: Acute and Subacute Oral Toxicity Studies in Rats.

NawaTab is a tablet formulation developed from the Nawametho polyherbal formula used in Surat Thani province, Southern Thailand, for the treatment of hyperlipidemia. This study aims at evaluating the acute and subacute toxicity of NawaTab in rats. In the acute toxicity study, NawaTab was evaluated in female rats following the OECD Guideline No. 423. In the subacute toxicity study, NawaTab was tested in both male and female rats following the OECD Guideline No. 407. In the acute toxicity study, no lethal effects or toxic signs were observed during the duration of the study. In the subacute toxicity study, there was no mortality and no abnormality in clinical signs, body weight, food consumption, relative organ weight, and hematological parameters of NawaTab-treated rats. Significantly increased water consumption by male rats (500 mg/kg BW) and female rats (250, 500, and 1000 mg/kg BW) was observed. In addition, globulin and total cholesterol of female rats (1000 mg/kg BW) significantly increased. These alterations were within normal physiological ranges. Moreover, necropsy and histopathological findings of NawaTab-treated rats demonstrated no obvious alterations attributable to NawaTab administration. The present study revealed that NawaTab has no significant acute oral toxicological effects. The lethal dose with a 50% mortality rate (LD50) was higher than 5000 mg/kg BW in rats. The subacute oral administration of NawaTab for 28 days did not have any major toxicological effects. Based on this study, NawaTab could be safe to use with caution pending its chronic toxicity study.

Uncontrolled Diabetes with Underlying Structural Changes in the Atrioventricular Node / Diabetes no Controlada con Cambios Estructurales Subyacentes en el Nodo Atrioventricular

SUMMARY: Diabetic cardiomyopathy, characterized by diabetes mellitus (DM) -induced cardiac muscular abnormalities, is a strong inducer of impaired cardiac contraction and arrhythmia. Atrioventricular block, a serious type of arrhythmia resulting from interruption of cardiac impulse conduction via the atrioventricular node (AVN), frequently occurs among diabetic patients. However, details of structural changes in AVN in DM remain poorly explained. Here, this study defined the effects of DM on the morphological remodeling of the AVN in male Sprague Dawley rats induced by intraperitoneal injection of streptozotocin (60 mg/kg body weight). At 24 weeks, the pathological changes in the AVN were assessed by light microscopy (LM) and transmission electron microscopy (TEM). Under LM, the AVN in diabetic rats became a less compact mass and exhibited the intracellular vacuolation. The nodal cells were more varied in sizes with the absence or shrinkage of nuclei and clear cytoplasm compared to the control. The collagen content significantly increased in relation to the presence of myofibroblasts. Consistent with LM, TEM images of the diabetic nodal cells revealed several signs of cell damage, such as mitochondrial changes, deterioration of cell organelles, gap junction internalization, and cell separation. Furthermore, changes in AVN innervation, evidenced by damaged Schwann cells and axons, were also found. These results indicated alterations in important components in the AVN during diabetic condition, which may lead to the impairment of electrical conduction, causing abnormal cardiac functions in diabetic patients.

La miocardiopatía diabética, caracterizada por anomalías musculares cardíacas inducidas por diabetes mellitus (DM), es un fuerte inductor de alteración de la contracción cardíaca y arritmia. El bloqueo atrioventricular, un tipo grave de arritmia resultante de la interrupción de la conducción del impulso cardíaco a través del nodo atrioventricular (NAV), se produce con frecuencia entre los pacientes diabéticos. Sin embargo, los detalles de los cambios estructurales en NAV en DM siguen estando pobremente explicados. Aquí, este estudio definió los efectos de la DM en la remodelación morfológica del NAV en ratas macho Sprague Dawley inducidas por inyección intraperitoneal de estreptozotocina (60 mg/kg de peso corporal). A las 24 semanas, los cambios patológicos en el NAV se evaluaron mediante microscopía óptica (MO) y microscopía electrónica de transmisión (MET). Bajo MO, el NAV en ratas diabéticas se convirtió en una masa menos compacta y exhibió la vacuolización intracelular. Las células nodales tenían tamaños más variados con ausencia o contracción de núcleos y citoplasma claro en comparación con el control. El contenido de colágeno aumentó significativamente en relación con la presencia de miofibroblastos. De acuerdo con MO, las imágenes MET de las células nodales diabéticas revelaron varios signos de daño celular, como cambios mitocondriales, deterioro de los orgánulos celulares, internalización de uniones comunicantes y separación celular. Además, también se encontraron cambios en la inervación del NAV, evidenciados por schwannocitos y axones dañados. Estos resultados indicaron alteraciones en componentes importantes en el NAV durante la condición diabética, lo que puede conducir al deterioro de la conducción eléctrica, causando funciones cardíacas anormales en estos pacientes.

Supplementation with the Traditional Thai Polyherbal Medicine NawaTab Ameliorates Lipid Profiles in High-Fat Diet-Induced Hyperlipidemic Rats.

A tablet formulation developed from Nawametho decoction (NawaTab), a traditional Thai herbal mixture described in the Worayokasan scripture, has been used clinically for several years in the management of borderline hyperlipidemic individuals. Nevertheless, scientific evidence supporting its claims has never been identified. This study aimed to describe the antihyperlipidemic properties of NawaTab in a well-described model of high-fat diet (HFD)-induced hyperlipidemic rats. Decoction of Nawametho containing equal quantities of Aegle marmelos (L.), Carthamus tinctorius L., Hibiscus sabdariffa Linn., Phyllanthus emblica L., Piper longum L., Piper nigrum L., Terminalia bellirica (Gaertn.) Roxb., Terminalia chebula Retz., and Zingiber officinale Roscoe were prepared. The HFD-fed rats were administered NawaTab for 4 consecutive weeks starting from the ninth week of HFD treatment at a dose of 125 mg/kg (p.o.). Anthropometric parameters, serum lipid profiles, lipase activity, and liver and renal functional markers were measured. Histopathological examination of the liver and any steatosis was carried out at the end of this study. Consecutive treatment with NawaTab (125 mg/kg/day) in HFD-induced hyperlipidemic rats caused a significant reduction in serum total cholesterol, triglyceride, low-density lipoprotein cholesterol, and very low-density lipoprotein cholesterol levels. However, at the tested dose, NawaTab failed to prevent the onset of hepatic steatosis and adipose tissue accumulation. No adverse events due to the consumption of NawaTab on liver and kidney function markers were noted. These findings are the first suggestive evidence for the lipid-lowering capability of NawaTab. However, to promote the use of this formulation in the management of borderline hyperlipidemic patients, elucidation of the underlying mechanisms of action, quantification of biological markers, and clinical trials of NawaTab are urgently needed.

The effects of early diabetes on duodenal alterations in the rats / Efectos de la diabetes temprana sobre las alteraciones duodenales en ratas

SUMMARY: Diabetes mellitus (DM) mainly affects functional changes in the duodenum, which plays an important role in the digestion and absorption of food. The impairment of duodenal function contributes to malnutrition, abdominal bloating and pain in diabetic patients. Thus, this study aimed to investigate the histological alterations and quantitative measurements of duodenal structures in the early stage of streptozotocin (STZ)-induced diabetic rats. Eight male Sprague-Dawley rats were divided into three control and five diabetic rats. Diabetes was induced by a single intraperitoneal dose of 60 mg/kg STZ. After four weeks of diabetic induction, the duodenum was prepared for histological study and morphometric analysis. In diabetic rats, there were deformed villi with disrupted surface epithelium and mildly distorted shapes of crypts, together with an increase in villus height and crypt depth. The epithelial cells detached from their underlying basement membrane. The goblet cells decreased in number, whereas an increased number of Cellula panethensis (Paneth cells) with pale-stained eosinophilic granules occurred in the DM group. A diabetic thickened submucosal layer was observed as enhanced duodenal glands (Brunner's glands) hypertrophy and collagen accumulation. These findings indicated that histopathologic lesions of the duodenum developed in the early stage of diabetes. The destruction of villi, crypts, and epithelium may affect digestion and absorption. The structural changes in goblet and Cellula panethensis and duodenal glands may be associated with malfunction to protect duodenal mucosa from bacteria and stomach acid. These conditions can worsen the quality of life in diabetic individuals, leading to complications such as maldigestion, malabsorption, and duodenal ulcer.

RESUMEN: La diabetes mellitus (DM) afecta principalmente a cambios funcionales en el duodeno, que juega un papel importante en la digestión y absorción de los alimentos. El deterioro de la función duodenal contribuye a la desnutrición, distensión abdominal y dolor en pacientes diabéticos. Por lo tanto, este estudio tuvo como objetivo estudiar las alteraciones histológicas y determinar las mediciones cuantitativas de las estructuras duodenales en la etapa temprana de ratas diabéticas inducidas por estreptozotocina (STZ). Ocho ratas macho Sprague-Dawley fueron distribuidas en dos grupos: tres ratas control y cinco diabéticas. La diabetes se indujo mediante una dosis intraperitoneal única de 60 mg/kg de STZ. Después de cuatro semanas de inducción, se preparó el duodeno para estudio histológico y análisis morfométrico. En ratas diabéticas, había vellosidades deformadas con epitelio superficial destruido y formas ligeramente distorsionadas de las criptas, junto con un aumento en la altura de las vellosidades y la profundidad de las criptas. Las células epiteliales se encontraban separadas de la membrana basal subyacente. Las células caliciformes habían disminuido en número, mientras que en el grupo DM se produjo un aumento en el número de Cellula panethensis (células de Paneth) con gránulos eosinofílicos teñidos pálidos. Se observó una capa submucosa engrosada con aumento de la hipertrofia de las glándulas duodenales (glándulas de Brunner) y acumulación de colágeno. Estos hallazgos indican que las lesiones histopatológicas del duodeno se desarrollaron en la etapa temprana de la diabetes. La destrucción de vellosidades, criptas y epitelio puede afectar la digestión y la absorción. Los cambios estructurales en Cellula panethensis y glándulas duodenales pueden estar asociados con un mal funcionamiento en la protección de la mucosa duodenal tanto de las bacterias como del ácido gástrico. Estas condiciones pueden empeorar la calidad de vida de las personas diabéticas y provocar complicaciones como mala digestión, malabsorción y úlcera duodenal.

Small bronchiolar histopathological changes related to prolonged diabetes / Pequeños cambios histopatológicos bronquiolares relacionados con la diabetes prolongada

SUMMARY: Diabetes mellitus increases the risk of developing chronic obstructive pulmonary disease (COPD). The small bronchiole is a prominent site of airflow obstruction that causes increased airway resistance in patients with the COPD. Therefore, the histological and ultrastructural changes in small bronchioles in streptozotocin (STZ)-induced chronic diabetes were determined. Twenty-four weeks after STZ induction, rats were sacrificed, and the right and left lungs were collected for examination by light and electron microscopy. The alterations to the small bronchioles were the same in both lungs of these diabetic rats. The bronchiolar epithelial cells, both ciliated and secretory club cells, showed pyknotic nuclei and damaged cytoplasmic organelles. Increased thickening of the bronchiolar wall occurred in diabetic rats due to smooth muscle layer thickening, inflammatory cell infiltration, and increased numbers of myofibroblasts with collagen deposition.These results indicated that chronic diabetes caused extreme damage to small bronchioles, which may lead to chronic small airway obstruction and ultimately increase the likelihood of COPD progression. This basic knowledge provides a better understanding of the progression of pathogenesis in the small airways of patients with prolonged diabetes.

RESUMEN: La diabetes mellitus aumenta el riesgo de desarrollar enfermedad pulmonar obstructiva crónica (EPOC). El bronquiolo es un sitio prominente de obstrucción del flujo de aire que causa una mayor resistencia de las vías respiratorias en pacientes con EPOC. Por lo tanto, se determinaron los cambios histológicos y ultraestructurales en los bronquiolos en la diabetes crónica inducida por estreptozotocina (STZ). 24 semanas después de la inducción de STZ, se sacrificaron las ratas y se analizaron los pulmones derecho e izquierdo por microscopía óptica y electrónica. Las alteraciones de los pequeños bronquiolos fueron las mismas en ambos pulmones de estas ratas diabéticas. Las células epiteliales bronquiolares, tanto ciliadas como secretoras, mostraban núcleos picnóticos y orgánelos citoplasmáticos dañados. Se produjo un aumento del engrosamiento de la pared bronquiolar en ratas diabéticas debido al engrosamiento de la capa de músculo liso, infiltración de células inflamatorias y un mayor número de miofibroblastos con colágeno. Estos resultados indicaron que la diabetes crónica causaba daño extremo a los pequeños bronquiolos, lo que puede conducir a una obstrucción crónica de las vías respiratorias pequeñas y además aumentar la probabilidad de progresión de la EPOC. Esta información proporcionará un mejor conocimiento de la patogénesis en las vías respiratorias pequeñas de los pacientes con diabetes prolongada.

Modifications of adrenal gland ultrastructure in streptozotocin-induced diabetic model rats / Modificaciones de la ultraestructura de la glándula suprarrenal en ratas modelo diabéticas inducidas por estreptozotocina

SUMMARY: The adrenal gland has been associated with the development of classical symptoms in diabetes mellitus (DM), including intensive polyuria and hyperglycemia. During DM, there are hormonal changes in the adrenal gland. Ultrastructural changes of adrenocortical and adrenal medulla cells and their effects on adrenocorticomedullary interaction have not been fully investigated. This study evaluated adrenocortical and adrenal medullary cells and adrenocorticomedullary interactions at ultrastructural levels in a streptozotocin-induced DM model, using transmission electron microscopy. Fifteen male, Sprague-Dawley rats were divided into diabetic model (n = 10) and control (n = 5) groups. Rats were sacrificed at four weeks after induction. The nuclei of some diabetic cortical cells were found to be irregularly shaped. In the cytoplasm, increased numbers of mitochondria and dilated smooth endoplasmic reticulum were observed. However, lipid droplets decreased in the DM model animals. The filopodia of diabetic cortical cells extended to contact the fenestrated capillary and other cortical cells and losses of gap junctions were also observed. Alterations of diabetic chromaffin cells resulted in similar appearances, consisting of irregularly shaped nuclei, swollen mitochondria, distended rough endoplasmic reticulum, and disrupted chromaffin vesicles. Examining adrenocorticomedullary interactions showed that the diabetic cortical chromaffin cells resembled those in the medulla. In the DM model group, collagen fibril depositions were observed between adrenal cells, especially near cell interactions. The filopodia of diabetic cortical cells were larger than those observed for diabetic adrenocorticomedullary interactions and adrenal cortex. These adrenal gland ultrastructural modifications represent contributions to the basic knowledge necessary for investigations of adrenal gland impairment during the early diagnosis of DM patients.

RESUMEN: La glándula suprarrenal se ha asociado con el desarrollo de síntomas clásicos en la diabetes mellitus (DM), que incluyen poliuria intensiva e hiperglucemia. Durante la DM, hay cambios hormonales en la glándula suprarrenal. Los cambios ultraestructurales de las células adrenocorticales y de la médula suprarrenal y sus efectos sobre la interacción adrenocorticomedular no se han investigado completamente. Este estudio evaluó las células adrenocorticales y de la médula suprarrenal y las interacciones adrenocorticomedulares a niveles ultraestructurales en un modelo de DM inducida por estreptozotocina, utilizando microscopía elec- trónica de transmisión. Se dividieron quince ratas macho Sprague- Dawley en grupos de modelo diabético (n = 10) y de control (n = 5). Las ratas se sacrificaron cuatro semanas después de la inducción. Se encontró que los núcleos de algunas células corticales diabéticas tenían una forma irregular. En el citoplasma, se observó un mayor número de mitocondrias y retículo endoplásmico liso dilatado. Sin embargo, las gotitas de lípidos disminuyeron en los animales modelo DM. Los filopodios de las células corticales diabéticas se extendieron para entrar en contacto con el capilar fenestrado y otras células corticales y también se observaron pérdidas de uniones gap. Las alteraciones de las células cromafines diabéticas dieron como resultado apariencias similares, que consistían en núcleos de forma irregular, mitocondrias inflamadas, retículo endoplásmico rugoso distendido y vesículas cromafines rotas. El examen de las interacciones adrenocorticomedulares mostró que las células cromafines corticales diabéticos se parecían a las de la médula. En el grupo del modelo de DM, se observaron depósitos de fibrillas de colágeno entre las células suprarrenales, especialmente cerca de las interacciones celulares. Los filopodios de las células corticales diabéticas eran más grandes que los observados para las interacciones adrenocorticomedulares diabéticas y la corteza suprarrenal. Estas modificaciones ultraestructurales de la glándula suprarrenal contribuyen al conocimiento básico para las investigaciones referente al deterioro de la glándula en el diagnóstico temprano de pacientes con DM.

Altered oligodendrocytes in spinal enlargements of streptozotocin diabetic rats / Oligodendrocitos alterados en la intumescencia espinal de ratas diabéticas con estreptozotocina

SUMMARY: Disturbances of sensory and motor nerve conduction velocity in the spinal cord as well as degenerated myelin sheaths are observed in diabetic patients and animal models. Indeed, oligodendrocytes (OLs), which are important neuroglial cells, generate myelin in the central nervous system. Spinal enlargement, including cervical and lumbar enlargements, innervates all limbs. Thus, the purposes of this study were to examine and compare the ultrastructural alterations of OLs in spinal enlargements of streptozotocin (STZ)- induced diabetic rats and controls. Thirteen male Sprague-Dawley rats were induced with STZ in citrate buffer and six control rats were injected with the same buffer solution. All rats were sacrificed after inductions at four (short-term DM) and twenty-four weeks (long-term DM). The selected spinal enlargements were processed for transmission electron microscopy. The OL alterations in both the cervical and lumbar enlargements were apparently the same. In short-term DM, the nuclei of OLs became swelled with chromatin clumping. Cytoplasmic organelles were moderately damaged. In long-term DM, OLs contained shrinkage nuclei with thick heterochromatin clumping. Severely degenerated mitochondria with disrupted cristae and broken membranes were observed. Moreover, distended and fragmented rough endoplasmic reticulum were observed, and large clear areas were present in the cytoplasm. Additionally, the loosening, splitting, and destruction of myelin lamellae were found. This study can provide important preliminary information about the alteration of OLs in the spinal cords of diabetic patients, which might be involve in the impairments of sensory and motor conduction velocities in these individuals.

RESUMEN: En pacientes diabéticos y modelos animales se observan alteraciones de la velocidad de conducción nerviosa sensorial y motora en la médula espinal, así como vainas de mielina degeneradas. De hecho, los oligodendrocitos (OL), que son importantes células neurogliales, generan mielina en el sistema nervioso central. La intumescencia espinal, a nivel cervical y lumbar, inerva los miembros. Por lo tanto, los propósitos de este estudio fueron examinar y comparar las alteraciones ultraestructurales de los OL en la intumescencia espinal de ratas diabéticas inducidas por estreptozotocina (STZ) y controles. Se indujeron trece ratas macho Sprague-Dawley con STZ en tampón citrato y se inyectaron seis ratas de control con la misma solución tampón. Todas las ratas se sacrificaron después de la inducción a las cuatro (DM a corto plazo) y a las veinticuatro semanas (DM a largo plazo). Las ampliaciones de la columna seleccionadas se procesaron para microscopía electrónica de transmisión. Las alteraciones de OL en las intumescencias cervical y lumbar eran aparentemente las mismas. En la DM a corto plazo, los núcleos de los OL se hincharon con la acumulación de cromatina. Los orgánulos citoplasmáticos sufrieron daños moderados. En la DM a largo plazo, los OL contenían núcleos de contracción con aglutinación de heterocromatina gruesa. Se observaron mitocondrias severamente degeneradas con crestas y membranas rotas. Además, se observó un retículo endoplásmico rugoso distendido y fragmentado, y estaban presentes grandes áreas claras en el citoplasma. Además, se encontraron el aflojamiento, la división y la destrucción de las laminillas de mielina. Este estudio puede proporcionar información preliminar importante sobre la alteración de los OL en la médula espinal de los pacientes diabéticos, que podría estar involucrada en las alteraciones de las velocidades de conducción sensorial y motora en estos individuos.

Cerebellar synaptopathy in streptozotocin-induced diabetic rats / Sinaptopatía cerebelosa en ratas diabéticas inducidas por estreptozotocina

SUMMARY: There is an increasing amount of evidence that supports the diabetic complications of the central nervous system structure and function. The cerebellum, which is one of the primary structure derived from the hindbrain, plays an important role in motor control, motor coordination, and non-motor functions, such as cognitive processing. The synapse is a critical structure that regulates neuronal communication, and well-defined afferent and efferent fibre connections in the cerebellum help in maintaining the proper working order. Thus, the present study sought to investigate the long-term effects of diabetes-induced synaptopathy in the cerebellum, using both histological and ultrastructural studies. Twenty Sprague-Dawley male rats were divided randomly into control and diabetic groups, and diabetes was then induced through a single intraperitoneal injection of streptozotocin (60 mg/kg body weight). Six month later, the rats were sacrificed and the cerebellum was removed. Light and electron microscopic examinations showed a degeneration of Purkinje cells (Neuron purkinjense) with shrunken cells, pyknotic nuclei, and synaptopathy, including the reduction in synapse density, number of synaptic vesicles, and maturation of synapses in the molecular layer of diabetic cerebellum. The disruptions in synaptic profiles, which observed in the diabetic condition, could be related to cerebellar dysfunction, thus leading to the defects in coordinated movement, balance, as well as cognitive learning and memory.

RESUMEN: Actualmente existe una creciente evidencia que apoya las complicaciones diabéticas de la estructura y función del sistema nervioso central. El cerebelo, una de las estructuras primarias del cerebro posterior, desempeña un papel importante en el control motor, la coordinación motora y las funciones no motoras, tanto como en el procesamiento cognitivo. La sinapsis es una estructura crítica que regula la comunicación neuronal y las conexiones de fibras aferentes y eferentes bien definidas en el cerebelo, ayudan a mantener el funcionamiento correcto. Por lo tanto, en el presente estudio se investigaron los efectos a largo plazo de la sinaptopatía inducida por la diabetes en el cerebelo, utilizando estudios histológicos y ultraestructurales. Veinte ratas SpragueDawley macho se dividieron al azar en grupos de control y diabetes, se indujó la diabetes a través de una inyección intraperitoneal única de estreptozotocina (60 mg / kg de peso corporal). Seis meses después, se sacrificaron las ratas y se extrajo el cerebelo. Los exámenes de microscopías óptica y electrónica mostraron una degeneración de las neuronas purkinjenses (células de Purkinje), con células reducidas, núcleos picnóticos y sinaptopatía, como también la densidad reducida de sinapsis, el número de vesículas sinápticas y la maduración de las sinapsis en la capa molecular del cerebelo de las ratas diabéticas. Las interrupciones en los perfiles sinápticos, que se observaron en la condición diabética, podrían estar relacionadas con la disfunción cerebelosa, lo que lleva a defectos en el movimiento coordinado, el equilibrio, así como al aprendizaje cognitivo y la memoria.

Arsenic impairs insulin signaling in differentiated neuroblastoma SH-SY5Y cells.

A strong correlation between chronic arsenic exposure and neuropsychological disorders leads to a growing concern about a potential risk of arsenic related neurodegeneration. Evidently, brain insulin signaling contributes to physiological effects, including energy homeostasis, and learning and memory. Arsenic has been shown to impair insulin signaling in adipocytes and myocytes, however, this impairment has not yet been explored in neurons. Here we showed that NaAsO2 caused significant reduction in basal levels of glucose, plasma membrane glucose transporter, GLUT 3 and Akt phosphorylation in differentiated human neuroblastoma SH-SY5Y cells. NaAsO2 significantly decreased insulin-mediated glucose uptake, as well as GLUT1 and 3 membrane translocation. Furthermore, the ability of insulin to increase Akt phosphorylation, a well-recognized insulin signaling response, was significantly lessened by NaAsO2 treatment. In addition, the classical tyrosine phosphorylation response of insulin was reduced by NaAsO2, as evidenced by reduction of insulin-induced tyrosine phosphorylation of insulin receptor (IR) and insulin receptor substrate-1(IRS-1). Moreover, NaAsO2 lowered the ratio of p110, a catalytic subunit to p85, a regulatory subunit of PI3K causing an imbalance between p110 and p85, the conditions reported to contribute to insulin sensitivity. Additionally, increment of IRS-1 interaction with GSK3ß, and p85-PI3K were observed in NaAsO2 treated cells. These molecular modulations may be mechanistically attributed to neuronal insulin signaling impairment by arsenic.

Paraquat induces extrinsic pathway of apoptosis in A549 cells by induction of DR5 and repression of anti-apoptotic proteins, DDX3 and GSK3 expression.

Paraquat (PQ) is a bipyridyl derivative herbicide known to cause lung toxicity partly through induction of apoptosis. Here we demonstrated that PQ caused apoptosis in A549 cells. PQ increased cleavage of caspase-8 and Bid, indicating caspase-8 activation and truncated Bid, the two key mediators of extrinsic apoptosis. Additionally, PQ treatment caused an increase in DR5 (death receptor-5) and caspase-8 interaction, indicating formation of DISC (death-inducing signaling complex). These results indicate that PQ induces apoptosis through extrinsic pathway in A549 cells. Moreover, PQ drastically increased DR5 expression and membrane localization. Furthermore, PQ caused prominent concentration dependent reductions of DDX3 (the DEAD box protein-3) and GSK3 (glycogen synthase kinase-3) which can associate with DR5 and prevent DISC formation. Additionally, PQ decreased DR5-DDX3 interaction, suggesting a reduction of DDX3/GSK3 anti-apoptotic complex. Inhibition of GSK3, which is known to promote extrinsic apoptosis by its pharmacological inhibitor, BIO accentuated PQ-induced apoptosis. Moreover, GSK3 inhibition caused a further decrease in PQ-reduced DR5-DDX3 interaction. Taken together, these results suggest that PQ may induce extrinsic pathway of apoptosis in A549 cells through upregulation of DR5 and repression of anti-apoptotic proteins, DDX3/GSK3 leading to reduction of anti-apoptotic complex.

Insulin attenuates arsenic-induced neurite outgrowth impairments by activating the PI3K/Akt/SIRT1 signaling pathway.

Arsenic neurotoxicity has a broad range of adverse effects on human health, which are induced in part by inhibition of neurite outgrowth. Insulin has been reported to promote neurite extension. The present study investigated whether insulin can protect neurons from impaired neurite outgrowth induced by arsenic, and examined the signaling pathway involved in this action. The study demonstrated that NaAsO2 caused inhibition of neurite outgrowth in differentiated SH-SY5Y cells indicating its neurotoxicity. This inhibitory effect of NaAsO2 was attenuated by insulin. It was found that blocking PI3K or Akt by selective inhibitors canceled the protective effect of insulin against NaAsO2-induced neurite outgrowth impairment suggesting the essential role of active PI3K and Akt in insulin's protective action. Inhibition of GSK3, which mimics an effect of insulin stimulation, had no effect on the impairment of neurite outgrowth by NaAsO2 implying that the insulin protective action is probably not due to its mediation of GSK3 inhibition ability. Moreover, NaAsO2 decreased the Akt activity, as it caused reduction in Akt phosphorylation, and downregulated expression of SIRT1. Additionally, the reduction of these signals by NaAsO2 was attenuated by insulin. Taken together, these results show that insulin attenuates arsenic-induced neurite outgrowth impairment possibly via activation of PI3K/Akt/SIRT1 signaling, and arsenic may exert neurite outgrowth inhibition through a mechanism involving reduction of signaling molecules downstream from insulin, PI3K/Akt/SIRT1. Our findings raise the possibility of using insulin to combat arsenic neurotoxicity.

Morphological and microvascular changes of the adrenal glands in streptozotocin-induced long-term diabetic rats.

It has been known that diabetes mellitus is associated with hyperfunction of the adrenal gland. However, the structural changes of adrenal gland in diabetes have rarely been studied. The aims of this study were to investigate the morphological and microvascular alterations in streptozotocin (STZ)-induced long-term diabetic rats. Twelve male Sprague-Dawley rats were divided into diabetic (n=8) and control (n=4) groups. Each diabetic rat was induced by an intraperitoneal injection of STZ (60 mg/kg) in citrate buffer (pH 4.5). Control rats were intraperitoneally injected with the same amounts of the buffer. These animals were sacrificed at 20 weeks after the injections. The adrenal glands were processed for the morphological and microvascular studies by using conventional light microscopy (LM) and vascular corrosion cast technique combined with scanning electron microscopy (SEM), respectively. In the diabetic group, the cells in zona glomeruloza (ZG) became atrophied and the thickness of this zone was found to be less than that of the controls. In the zona fasciculata (ZF) and zona reticularis (ZR), the hypertrophic cells were investigated in both layers. The degenerated chromaffin and hypertrophic sympathetic ganglion cells in the adrenal medulla were observed. Also some degenerated ganglion cells were found. Additionally, lymphocyte infiltration, macrophages and amyloidosis were found in the adrenal medulla of long-term diabetic rats with renal failure. Under the SEM observation, the luminal diameters of capillaries in the diabetic group were dilated in all zones. In addition, these capillaries in the ZF and ZR were arranged in tortuous courses. This study demonstrates morphological and microvascular changes in the adrenal gland of diabetic rats which are in accordance with the hormonal changes reported by previous investigators.

Unique cellular structures in the parotid gland of an Old world fruit bat, Pteropus lylei (Lyle's flying fox).

Pteropus lylei (Lyle's flying fox), an Old World fruit bat, consumes only ripe fruit, which contains low protein and sodium. The carpophagous diet of P. lylei presents an adaptive challenge for salivary glands to conserve sufficient nutrition for living. Therefore, the parotid glands in both sexes were investigated by using light microscopy and transmission electron microscopy. No structural difference was observed in the parotid glands between sexes. The acinar cell contained dense serous secretory granules, prominent luminal microvilli and intercellular canaliculi. The intercalated duct exhibited simple cuboidal epithelium with no secretory granule. Striated duct consisted of simple columnar epithelium with basal striation, numerous elongated mitochondria, and apical vesicles. In the interlobular duct, simple tall columnar epithelium and apocrine secretion were found. The interlobar and excretory ducts surprisingly contained continuous capillaries that intervened in stratified cuboidal epithelium. In addition, there were several blood vessels around the interlobular, interlobar and excretory ducts. The morphological adaptation of the parotid gland observed in P. lylei enables this species to obtain sufficient nutrients from the preferred consumption of ripe fruit. Serous secretory granule was suitable for digestion of ripe fruit. A well-developed striated duct, continuous capillaries among the epithelial cells of interlobar and excretory ducts, and numerous blood vessels around these ducts enhanced the reabsorption of amino acids and ions. Structural variations in the parotid gland can indicate not only a correlation to diet and survival but also a close relationship of the Old World fruit bat to other kinds of bats.